Yakutia SU95 at Yakutsk on Oct 10th 2018, overran runway on landing
Last Update: October 9, 2020 / 18:34:29 GMT/Zulu time
Date of incident
Oct 10, 2018
SUKHOI Superjet 100-95
ICAO Type Designator
Yakutsk Airport, Yakutsk
Airport ICAO Code
Rosaviatsia (Russia's CAA) reported the aircraft with 87 passengers and 5 crew had performed the flight from Ulan-Ude to Yakutsk when it rolled beyond the runway end resulting in the collapse of the main landing gear. There were no injuries. Rosaviatsia opened an investigation into the occurrence.
The aircraft manufacturer reported the cause of the accident were external factors. Sukhoi is going to provide all requested assistance to the investigation.
The airline reported the aircraft overran the end of the runway while landing in Yakutsk, the aircraft was evacuated via slides. Four people requested medical assistance for bruises and headache. A commission has been formed to investigate the accident.
According to local sources ATC reported standard braking action to the crew, which did not meet the actual icy/slippery condition of the runway. ATC in turn had not been informed about the deteriorating condition of the runway.
Rosaviatsia later released first preliminary information stating the aircraft went went through a work barrier about 150 meters past the (displaced) runway end, went over the edge between new and old runway surface about 30 meters past the barrier and came to a stop 65 meters past the edge. At 04:50L the braking coefficients were measured at: 0.27, 0.32, 0.25 (average 0.28), at 05:25L: 0.25, 0.32, 0.25 (average 0.27)
On Oct 10th 2018 the Interstate Aviation Committee (IAC, aka MAK) announced they have opened an investigation into the accident of RA-89011.
On Oct 11th 2018 Rosaviatsia reported in their Flight Safety Bulletin 19, that the friction coefficients of runway 23L had been estimated at 0.45, this value was also transmitted to the crew. Following the occurrence the runway was inspected and ice was found on the runway, the friction values were determined at 0.25/0.32/0.25 (average 0.27), which may indicate improper maintenance of aerodrome components to keep them in operational conditions. The runway was undergoing reconstruction work since May 2018, the threshold of runway 05R had therefore been displaced by 1150 meters leaving a landing distance of 2248 meters available on runway 23L. The aircraft rolled about 250 meters past the end of runway 23L resulting in the destruction of main gear legs and damage to the power plants. The aircraft had been dispatched under minimum equipment list requirements with the right hand reverser being inoperative. The MEL permits landing only with a runway friction coefficient at 0.4 or above.
On Oct 9th 2020 the Interstate Aviation Committee (MAK) released their final report in Russian only (Editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a Russian only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).
The report concludes the probable cause of the accident was:
the transmission of an incorrect braking coefficient, while the runway was at a coefficient of less than 0.3 preventing any landing on the runway, which misled the crew to continue with the landing with a thrust reverser inoperative. This led to a significant increase of the landing distance required, caused the overrun of the runway end and collision with the intersection of reconstructed part of the runway with the joint at height differences of 0.4m and the destruction of the landing gear, a fuel leak occurred however no fire.
Contributing factors were:
- Lack of a connecting ramp at the joint between active and reconstructed runway sections
- inefficiency of Yakutsk Airport with respect to detecting and control risks associated with ice
- mistaken definition of the braking coefficient during last runway friction measurement
- inefficiency of ice removal from the runway due to lack of chemical reagents or thermal machines to remove the ice
- lack of information by the crew of another SU95 (RA-89038) that they had overrun the runway
- lack of reaction by ATC and airport officials to the complaint by the crew of RA-89038 about the low braking action
The MAK reported the aircraft collided with the reconstructed and by 0.4 meters elevated section of the runway at about 40-50 kph (22-27 knots), the gear collapsed, the aircraft continued on the reconstructed section of the runway coming to a stop about 60 meters past the joint and about 360 meters past the runway end. The passengers were evacuated via slides.
The MAK reported that about 2 hours prior to the landing of RA-89011 another SU95 registration RA-89038 landed on Yakutsk's runway 23L but overran the end of the runway despite use of thrust reversers and applying the parking (emergency) brakes. The aircraft turned around on the runway and vacated the runway via taxiway D, then stopped reporting slippery conditions and requested to be towed to the apron. After arrival at the apron damaged tyres were found. According to FDR the aircraft had touched down 360 meters past the threshold of the runway at 132 KIAS, autobrakes and spoilers engaged, the thrust reversers were brought into the maximum reverse position. The crew reduced reverse and began to apply manual braking at 88 knots at about 1200 meters past the threshold, the brakes pressure increased to about 550-600 psi instead of 3000psi indicating the low braking action of the runway, the crew commented they had no brakes and applied full thrust reverse again about 1450 meters past the threshold. Slowing through 68 knots the FDR recorded the park brakes being applied, which increased the brakes pressure to 3000 psi but disabled the anti-skid system. The reverse thrust was reduced. The crew commented again that they had no brakes. Slowing through 30 knots the crew again applied full reverse thrust. The aircraft began to turn left with all brakes at 3000 psi, maximum reverse thrust. The aircraft went past the runway end and came to a stop about 60-70 meters past the runway end at a heading of 148 degrees. After coming to a stop the crew stowed the thrust reversers and released the park brakes.
The MAK reported that the talks of the crew between them clearly suggest they were aware of the runway overrun but decided to not report it. The crew reported in interviews they did notice the runway end lights but didn't feel the aircraft went past the end of the runway.
The MAK analysed that the right hand thrust reverser had been locked out and was unavailable for the landing on RA-89011. The landing speed of RA-89011 was computed at Vref=149 KIAS. Based on ATC report the crew selected medium autobrakes and briefed to use reverse thrust at maximum as long as possible. The FCOM recommended to not use the autobrakes on slippery runways due to the possibility of uneven braking (different brakes pressure applied by anti-skid).
The MAK reported the crew was told the braking coefficient was 0.45 (also radioed via ATIS) with a tailwind of 6 knots with a dry runway, the landing distance required in these conditions (dry concrete runway) at 0.45 braking coefficient was 1100 meters, with reverse thrust available from one or both engines being an additional bonus. The decision to continue landing thus was reasonable.
The crew applied full flaps for the landing.
The approach was stable. The aircraft crossed the runway runway threshold at 35 feet AGL at 145 KIAS and touched down at 5 degrees nose up pitch at 144 KIAS about 360 meters past the runway threshold and lowered the nose gear onto the runway about 4 seconds after the main gear touch down. The thrust reversers were deployed, the right hand thrust reverser remained in its locked/non deployed position and the right hand engine remained in idle thrust, the left hand thrust reverser spooled up. The autobrakes activated, the brakes pressure increased without brakes pedal activation.
The crew should not have used autobrakes however, this was no factor into the sequence of events though it increased a risk for safety.
The crew, after applying maximum thrust reverse, stowed the (left) reverser at 100 KIAS. This early stowage of the thrust reverser was not a compentent decision by the crew.
1550 meters past the runway threshold the aircraft was still travelling at 90 knots, the average deceleration has not been more than 1.4m/s/s. Upon reaching 85 knots the crew called out "no deceleration" and the crew applied brakes pedals. The crew again noticed ineffective braking, with the crew applying maximum brakes on the brakes pedals the left thrust reverser was again activated and maximum reverse thrust commanded. The aircraft went past the runway end at 47 knots (87 kph), the nose gear collided with the step at the intersection at 26 knots (48 kph). At about the time of that collision the crew stowed the left thrust reverser. The main landing gear impacted the runway step at 21 knots (39 kph) resulting in a maximum vertical acceleration of +4.38G. The main gear collapsed, also evidenced by the FDR recording the aircraft no longer in ground mode. The aircraft skidded on the reconstructed runway, came to a stand still about 60 meters past the joint. Shortly after coming to a stop fire indications for both engines activated caused by the fractures of both wiring harnesses A and B at the wing attachment points of the landing gear struts, no actual fire occurred. The captain instructed the engines being shut down and ordered the evacuation of the aircraft to the left as he was sure there was no fire. However, the evacuation did not commence until 5 minutes later after the lead flight attendant had inquired with the cockpit.
The MAK analysed that the landing distance required for the conditions reported was 1100 meters, with the safety margin (factor 1.21) added 1331 meters. For the braking coefficient less than 0.3 however these values needed to be multipled by 2.47 (with safety marking 3288 meters landing distance required).
Although the medium autobrakes should have provided a deceleration of 2.4 meters/s/s, the aircraft acutally achieved only 1.46 m/s/s also confirming the braking coefficient being below 0.3. The brakes pressure applied by the autobrakes of about 300-400 psi also confirmed the low braking coefficient.
When the crew changed from autobrakes to manual braking via the brakes pedals, the brakes pressure hardly changed with anti-skid continuing to operate.
A comparison of both landing performances (RA-89038 and RA-89011) showed that 89011 landed at 12 knots faster than 89038 mainly due to external factors (winds). Otherwise the aircraft touched down at about the same spot, their decelerations were about the same, 89038 came to a stop 1978 meters past touchdown while 89011 collided with the runway step 2048 meters after touchdown. Even the use of both thrust reversers was not benefitial to 89038 due to the fact that the crew applied emergency brakes und thus disengaged anti-skid causing the aircraft to glide on the runway.
Yakutsk Airport planned to renovate the surface of the runway without suspending activities. The reconstruction was to apply two layers of 20cm concrete each onto the runway, the new runway surface thus was 40cm above the old surface. About 30 meters prior to the reconstruction zone a temporary a temporary fence was installed. A small ramp for construction vehicles was erected at the joint of old and new runway, however, not along the full width of the runway. The works as well as the plan had been approved.
The issue of a ramp however had been brought up during planning the reconstruction work suggesting a temporary asphalt ramp over a length of 300-350 meters before the joint. However, the suggestion was not taken up, in particular also because it had been planned to complete the reconstruction work before the winter period (in which the accident happened). The plan thus did not take into account winter conditions.
The MAK analysed that the runway friction coefficient was below 0.3 already at the time of RA-89038 overruning the runway and did not change much. A runway measurement had been taken prior to the arrival of both aircraft with no significant changes of the weather thereafter. The equipment to measure the runway friction was working according to specification, no faults were recorded with the equipment. The engineer subsequently reported a runway friction coefficient of 0.45 - the MAK analysed that the engineer spent sufficient time on the runway to carry out the measurement with the working equipment. The MAK analysed that there was no significant change of runway friction possible following the measurement and such analysed that at the time of measurement the coefficient was below 0.3 already.
The commission was unable to determine the source of error, how the engineer determined 0.45 despite the measurements suggesting less than 0.3. The MAK analysed that the ATT-2 model used by the engineer was outdated, however, could not explain that error.
The MAK conducted a surprise visit to the aerodrome to verify the operations to clear the runway. The visit showed that the runway was cleared, however, no chemical agent or thermal machine was being used to remove ice. Ice removal thus was impossible, the risks had been considered but not taken into account, oversight by aviation authority was thus inadequate.
UEEE 092030Z 06004MPS 9999 BKN014CB M04/M06 Q1011 R23L/590129 NOSIG RMK QFE750=
UEEE 092000Z 07003MPS 9999 BKN014CB M04/M06 Q1011 R23L/590145 NOSIG RMK QFE750=
UEEE 091930Z 06002MPS 9999 BKN014CB M03/M05 Q1012 R23L/590145 NOSIG RMK QFE750=
UEEE 091900Z 06003MPS 9999 BKN015CB M03/M05 Q1012 R23L/590145 NOSIG RMK QFE750=
UEEE 091830Z 05003MPS 9999 BKN020CB M03/M04 Q1012 R23L/590145 NOSIG RMK QFE750=
UEEE 091800Z 05002MPS 9999 BKN020CB M03/M04 Q1012 R23L/590145 NOSIG RMK QFE750=
UEEE 091730Z 04002MPS 9999 BKN021CB M03/M04 Q1012 R23L/590145 NOSIG RMK QFE751=
UEEE 091700Z 04002MPS 9999 BKN020CB M03/M04 Q1013 R23L/590145 NOSIG RMK QFE751=
UEEE 091630Z 04002MPS 9999 SCT010 OVC019CB M03/M04 Q1013 R23L/590145 NOSIG RMK QFE751=
UEEE 091600Z 04002MPS 9999 SCT011 OVC022CB M02/M03 Q1013 R23L/590145 NOSIG RMK QFE751=
UEEE 091530Z 01001MPS 9999 SCT011 OVC022CB M02/M03 Q1013 R23L/590145 NOSIG RMK QFE751=
A5724/18 NOTAMR A4144/18
A) UEEE B) 1810010730 C) 1810312359
E) 1. RWY 05R THR DISPLACED BY 1150M TOWARDS ARP DUE TO RECONSTRUCTION.
2. TWY A AND TWY B CLSD.
3. TWY C CLSD FOR AIRPLANES TAX.
4. CONSTRUCTION EQPT HGT UP TO 4M OPR AT RWY 05R/23L SEGMENT UNDER RECONSTRUCTION.
5. RWY 05R AVBL FOR TKOF ONLY. DECLARED DIST: TORA 2248M, TODA 2698M, ASDA 2248M.
6. RWY 23L AVBL FOR LDG ONLY. LDA 2248.
7. ACFT CREW IS AUTHORISED, BY COORDINATION WITH ATS, TO PERFORM TKOF FROM RWY 23L PROVIDED THAT CONSTRUCTION EQPT ON RWY 05R/23L OPR AT DIST NOT LESS THAN 2680M FROM RWY 23L THR.
A5725/18 NOTAMR A4038/18
A) UEEE B) 1810010740 C) 1810312359
E) 1. RWY 05R: LIGHTING FAC U/S.
2. RWY 05R/23L: RCLL U/S.
3. RWY 23L: TDZ LIGHTS U/S.
A5565/18 NOTAMR A2986/18
A) UEEE B) 1809250640 C) 1810302359
E) RWY 23L: ILS U/S.
Date of incident
Oct 10, 2018
SUKHOI Superjet 100-95
ICAO Type Designator
Yakutsk Airport, Yakutsk
Airport ICAO Code
This article is published under license from Avherald.com. © of text by Avherald.com.
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